Frame for mine roof support



United States Patent 3,097,727 FRAME FOR MINE ROOF SUPPORT Karl Theodor Jasper, Grnnstrasse 36a, and Hans Werner vom Felde, Ruhrstrasse 17, both of Hagen, Germany Filed Nov. 19, 1958, Ser. No. 774,917 Claims priority, application Germany Nov. 23, 1957 2 Claims. (Cl. 189-34) The invention relates to frames for underground mine roof support, and is particularly concerned with a channelsection roof support consisting of a plurality of segments which are arranged in one another at their ends and are resiliently clamped to one another by frictional locking over parts of their surfaces, and which are of identical or symmetrical cross-section, with the outer and inner envelope ourves following a parabolic course.

As is known, the segments of a channel-section roof support of this kind have congruent or symmetrical crosssections, whose envelope curve line provides the necessary conditions for permitting the individual sections to be arranged in one another in any desired sequence.

The inter-engaged ends of two segments are clamped fast against one another by means of connecting elements which engage more or less far about them, the inner side of one section coming to bear wholly or partly against the outer side of the other section, so that telescopic sliding of the individual segments in one another in the direction of their longitudinal axes under the influence of roof pressure is only possible when the frictional resistance between the parts of the two segments bearing against one another produced by the clamping action has been overcome. However, the clamping force can only be taken as high as is allowed by the material properties of the clamping means, more particularly the elasticity thereof, since when known channel sections are used these come to bear against one another in the region of their base surfaces or flange surfaces, so that in a connection of this kind only the actual bearing surface of two segments is available as a frictional engagement surface.

The already known constructional forms of channelsection roof supports have proved extremely valuable both in the form comprising complementary but non-identical segments and also in the form of an arch comprising identical segments of identical or symmetrical cross-section, which is the form nowadays used almost exclusively. However, the manufacture thereof requires maintaining relatively close rolling tolerances, since in these sections either the section flanges and parts of the side webs, or else the section bottoms and possibly also parts of the section webs bear against one another, and if the fit of the two sections when clamped against one another is defective the result is that the available bearing surface, i.e. frictional engagement surface, is dependent on too many contingencies, so that loading conditions vary very much.

-'In the known box-construction identical sections, a negative tolerance difference at the outer section and a positive tolerance difference at the inner section for example has the result that about the edges of the inner section bearing against the webs of the outer section the webs of the former bend outwardly under the action of the clamping force and the webs of the outer section bend inwardly, without, however, the two surfaces coming to bear flush against one another.

With identical sections constructed with bell-shaped cross-sections, on the contrary, the transmission of force between two sections arranged one within the other is more uniform, even though here owing to the discontinuous outer envelope curve of the section a close fit between section webs and bottoms is ensured only if relatively close rolling tolerances are maintained.

In realisation of these inter-connections in hitherto conventional yieldable mine roof supports composed of chan- 3,097,727 Patented July 16, 1963 nel sections the invention provides a roof support which can be produced in a particularly economical manner whilst not requiring the maintenance of close tolerances when rolling the sections, and yet which is capable of accepting the roof pressure forces and providing the desired resistance thereto, without thereby restricting the yieldability of the roof support which comes itno effect during the course of pressure acceptance.

According to the invention, the roof support section is so shaped that the inner envelope curve parabola of the channel section is taken to the apex of the section bottom, whereas the outer envelope curve parabola in the region of the section bottom merges into an arc, so that the sections when laid in one another are in areal contact only in the parabolic regions of their webs.

Since in the novel section the envelope curve of the cross-section, more particularly the outer curve, is continuous, the advantages of channel sections whose envelope curves are formed of parabolas, consisting of particularly high resistance to the different kinds of load to which the section may be subjected in many different ways, are augmented by the further advantage that in addition to the friction the material elasticity of the support segments is now utilised to a much greater extent, since the two sections arranged one within the other bear flush against one another at their webs, and, with increasing clamping force or pressure acceptance, slide elastically together more and more transversely to the longitudinal axis of the segments, the outer section in each case being stressed in the divergent sense and the inner section in each case being stressed in the convergent sense within the range of elastic deformation. Under these circumstances, until the range of permanent deformation of the sections is reached, neither the lateral flanges of the sections nor the section bottoms contact one another, which in any case would reduce if not eliminate altogether the utilisation of the elasticity inherent in the material. The resistance to gaping in the X-axis of the sections which thereat becomes effective is strong enough, owing to the extremely advantageous distribution of mass in a section of this kind, to meet fully the requirements expected of it.

According to a particularly advantageous form of embodiment of the novel section, the outer envelope curve of the section cross-section is so constructed that its parabola merges ino an arc below a theoretical tangent drawn at the apex of the section bottom to the inner envelope curve parabola.

A particularly economical advantage of the support according to the invention is seen to reside in the fact that the envelope curve shape of the section permits the novel section to be used readily with any corresponding other section having a parabolic envelope curve, more particularly a section whose flanges and/or bottoms come to bear against one another when two sections are clamped together, the advantages of the hitherto conventional support sections of bell-shaped cross-section being augmented by a further particularly important advantage.

The novel construction of the bell section affords also the extremely advantageous possibility of shifting the X-axis into centre line of the section, so that the W and W values and also the corresponding inertia values can be brought substantially nearer one another in the sense of maximum equalisation thereof.

The drawing shows a sectional view of a support constructed according to the invention for a mine roof support structure consisting of channel sections.

As the drawing shows, the inner sides 1 and the outer sides 2 of the two sections 6 and 7 which are arranged one within the other are shaped in accordance with a parabola which advantageously obeys the formula 0.4 x In this case the inner envelope curve parabola 1 of the section is taken to the apex point 3 of the section bottom 4, whereas on the other hand the outer envelope curve parabola 2 merges, in the region of the section bottom 4, into an arc 5 whose connection point is below the theoretical tangent drawn to the inner parbola '1 at the apex point 3 of the section bottom 4. The outer and inner envelope curves of the section diverge in the direction of the section bottom 4.

The outer section 6 and the inner section 7 are in areal contact against one another in the region of their webs 8, the contacting surface between the two being all the greater the more effective the clamping force on the sections 6 and 7 is. Neither the section bottoms 4 nor the section flanges 9 are in contact with one another.

Of course the novel channel section can be produced for any desired number of weight classes using the same rolls, merely varying the spacing of the two surfaces of the rolls from one another.

We claim:

1. Roof support frame for underground mine roof support or the like comprising a plurality of segments comprising channel sections of identical or symmetrical crosssection, which are arranged in one another at their ends and are clamped yieldably to one another by frictional locking over parts of their surfaces, and whose outer and inner envelope curves follow a parabolic course, the inner parabolic envelope curve being taken to the apex point of the section bottom, characterised in that the outer parabolic envelope curve merges into an arc in the region of the section bottom so that the sections when arranged one within the other are in areal contact only at the parabolic regions of their webs.

2. Roof support frame according to claim 1, characterised in that the outer parabolic envelope curve merges into an arc below the theoretical tangent drawn to the inner parabolic envelope curve at the apex point of the section bottom.

References Cited in the file of this patent German printed application of Hennlich, Serial No. H 15,185 V-I/5c, August 23, 1956. 

1. ROOF SUPPORT FRAME FOR UNDERGROUND MINE ROOF SUPPORT OR THE LIKE COMPRISING A PLURALITY OF SEGMENTS COMPRISING CHANNEL SECTIONS OF IDENTICAL OR SYMMETRICAL CROSSSECTION, WHICH ARE ARRANGED IN ONE ANOTHER AT THEIR ENDS AND ARE CLAMPED YIELDABLY TO ONE ANOTHER BY FRICTIONAL LOCKING OVER PARTS OF THEIR SURFACES, AND WHOSE OUTER AND INNER ENVELOPE CURVES FOLLOW A PARABOLIC COURSE, THE INNER PARABOLIC ENVELOPE CURVE BEING TAKEN TO THE APEX POINT OF THE SECTION BOTTOM, CHARACTERIZED IN THAT THE OUTER PARABOLIC ENVELOPE CURVE MERGES INTO AN ARC IN THE REGION OF THE SECTION BOTTOM SO THAT THE SECTIONS WHEN ARRANGED ONE WITHIN THE OTHER ARE IN AREAL CONTACT ONLY AT THE PARABOLIC REGIONS OF THEIR WEBS. 